What are the causes of zinc deficiency?
A poor diet can cause zinc deficiency. So it is more common in malnourished children and adults and in people who are unable to eat a normal diet due to circumstances or illness. Lots of zinc intake is from meat and seafood, so vegetarians may be more prone to deficiency. The greater demand caused by pregnancy and breast-feeding may also cause zinc deficiency.
Problems with the guts can lead to problems absorbing zinc. This includes gut conditions such as ulcerative colitis, Crohn's disease, and coeliac disease, and conditions where there is persisting diarrhoea.
People who drink excessive alcohol can also not absorb zinc normally. Long-term illnesses, such as chronic liver or kidney disease can also result in low absorption of zinc. High-dose iron supplements can also affect the way zinc is absorbed, leading to deficiency.
A rare inherited condition called acrodermatitis enteropathica is an occasional cause of zinc deficiency. In this condition, there is an absence of a transport protein which normally allows zinc absorption, resulting in severe deficiency. Where this is the case, symptoms begin soon after a baby is weaned off breast milk. A typical rash is often the first symptom.
What are the causes of zinc excess?
The most common cause of zinc excess is taking too many zinc supplements. It is important not to take more than the advised dose.
Other causes are less common. If your kidneys are not working well (for example, if you have acute kidney injury) they do not get rid of excess zinc for you. In this case it can accumulate. Acute kidney injury does not mean you have had a physical trauma to your kidney; it is a sudden loss of kidney function, usually due to an illness such as a severe infection.
If you have an uncommon condition called haemochromatosis, you are more likely to get zinc overload. This is because you have high levels of iron, which can affect the way that zinc is absorbed and used.
Certain industrial compounds have high levels of zinc, and it is occasionally possible to get zinc poisoning through exposure to these substances. These include some pesticides and some components used in paints, dyes and rubber.
Further reading and references
Evans JR, Lawrenson JG; Antioxidant vitamin and mineral supplements for slowing the progression of age-related macular degeneration. Cochrane Database Syst Rev. 2012 Nov 1411:CD000254. doi: 10.1002/14651858.CD000254.pub3.
Singh M, Das RR; Zinc for the common cold. Cochrane Database Syst Rev. 2013 Jun 186:CD001364. doi: 10.1002/14651858.CD001364.pub4.
Lazzerini M, Wanzira H; Oral zinc for treating diarrhoea in children. Cochrane Database Syst Rev. 2016 Dec 2012:CD005436. doi: 10.1002/14651858.CD005436.pub5.
Allan GM, Arroll B; Prevention and treatment of the common cold: making sense of the evidence. CMAJ. 2014 Feb 18186(3):190-9. doi: 10.1503/cmaj.121442. Epub 2014 Jan 27.
Saper RB, Rash R; Zinc: an essential micronutrient. Am Fam Physician. 2009 May 179(9):768-72.
Zinc. Consumer Fact Sheet; National Institute of Health Office of dietary supplements
Acrodermatitis enteropathica; DermNet NZ
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